The present disclosure relates generally to gas turbine engines and, more particularly, to a rotor support system for a gas turbine engine having a shape memory alloy.
Gas turbine engines typically include a rotor assembly, a compressor, and a turbine. The rotor assembly includes a fan that has an array of fan blades extending radially outward from a rotor shaft. The rotor shaft transfers power and rotary motion from the turbine to both the compressor and the fan, and is supported longitudinally using a plurality of bearing assemblies. Additionally, the rotor assembly has an axis of rotation that passes through a rotor center of gravity. Known bearing assemblies include rolling elements and a paired race, wherein the rolling elements are supported within the paired race. To maintain a rotor critical speed margin, the rotor assembly is typically supported on three bearing assemblies, one of which is a thrust bearing assembly and the other two are roller bearing assemblies. The thrust bearing assembly supports the rotor shaft and minimizes axial and radial movement of the rotor shaft assembly. The remaining roller bearing assemblies support radial movement of the rotor shaft.
During operation of the engine, sometimes a fragment of one of the fan blades may become separated from the remainder of the blade through fan blade out event. Accordingly, a substantial unbalanced rotary load may be created within the damaged fan thus creating substantial rotor imbalances. Such rotor imbalances must be carried substantially by shaft bearings, bearing supports, and support frames. Further, fan blade out may also cause the engine to operate with a lesser capability, necessitating repair.
To minimize the effects of potentially damaging, abnormal unbalanced loads, gas turbine engines often include support components for the fan rotor support system that are sized to provide additional strength. However, increasing the strength of the support components increases an overall weight of the engine and decreases an overall efficiency of the engine under its normal operation without substantial rotor imbalances. To address abnormal unbalanced load, the engines may also utilize a bearing support that includes a mechanically weakened section, or primary fuse, that decouples the fan rotor from the fan support system. During such events, the fan shaft seeks a new center of rotation that approximates that of its unbalanced center for gravity. This fuse section, in combination with a rotor free orbit allowance, is referred to as a load reduction device (LRD). The LRD reduces the rotating dynamic loads in the fan support system. However, with conventional LRDs, the fan rotor is permanently decoupled from the fan rotor support system when the primary fuse fails. As a result, subsequent operation of the gas turbine engine may be significantly impacted.
Accordingly, an improved rotor support system that is configured to accommodate unbalanced or increased loading conditions without resulting in a permanent decoupling of the fan rotor from the rotor support system would be desirable.